[petsc-users] GMRES for outer solver

Amneet Bhalla mail2amneet at gmail.com
Sun May 1 00:03:14 CDT 2022

How about using a fixed number of Richardson iterations as a Krylov
preconditioner to a GMRES solver? Would that lead to a linear operation?

On Sat, Apr 30, 2022 at 8:21 PM Jed Brown <jed at jedbrown.org> wrote:

> In general, no. A fixed number of Krylov iterations (CG, GMRES, etc.) is a
> nonlinear operation.
> A fixed number of iterations of a method with a fixed polynomial, such as
> Chebyshev, is a linear operation so you don't need a flexible outer method.
> Ramakrishnan Thirumalaisamy <rthirumalaisam1857 at sdsu.edu> writes:
> > Hi,
> >
> > I have a Krylov solver with a preconditioner that is also a Krylov
> solver.
> > I know I can use "fgmres" for the outer solver but can I use gmres for
> the
> > outer solver with a fixed number of iterations in the Krylov
> > preconditioners?
> >
> >
> > Thanks,
> > Rama
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